system: Tell module-init-tools where to look for modules.

* gnu/packages/linux.scm (module-init-tools)[source](patches): New
  field.
* gnu/packages/patches/module-init-tools-moduledir.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/system.scm (etc-directory): Add #:kernel parameter.  Set
  'LINUX_MODULE_DIRECTORY' in bashrc.
  (operating-system-etc-directory): Pass #:kernel to 'etc-directory'.

gnu-system.am

@@ -331,6 +331,7 @@ dist_patch_DATA =						\
   gnu/packages/patches/mhash-keygen-test-segfault.patch		\
   gnu/packages/patches/mit-krb5-init-fix.patch			\
   gnu/packages/patches/mpc123-initialize-ao.patch		\
+  gnu/packages/patches/module-init-tools-moduledir.patch	\
   gnu/packages/patches/openssl-CVE-2010-5298.patch		\
   gnu/packages/patches/openssl-extension-checking-fixes.patch	\
   gnu/packages/patches/patchelf-page-size.patch			\

gnu/packages/linux.scm

@@ -133,7 +133,9 @@
                    version ".tar.bz2"))
              (sha256
               (base32
-               "0jxnz9ahfic79rp93l5wxcbgh4pkv85mwnjlbv1gz3jawv5cvwp1"))))
+               "0jxnz9ahfic79rp93l5wxcbgh4pkv85mwnjlbv1gz3jawv5cvwp1"))
+             (patches
+              (list (search-patch "module-init-tools-moduledir.patch")))))
     (build-system gnu-build-system)
     (arguments
      ;; FIXME: The upstream tarball lacks man pages, and building them would

gnu/packages/patches/module-init-tools-moduledir.patch

@@ -0,0 +1,168 @@
+This patch changes 'modprobe' & co. so they honor the 'LINUX_MODULE_DIRECTORY'
+environment variable, rather than looking for modules exclusively in
+/lib/modules.
+
+Patch by David Guibert, from Nixpkgs; adjusted to use 'LINUX_MODULE_DIRECTORY'
+rather than 'MODULE_DIR' as the variable name.
+
+commit cf2c95edb7918bc658f6cae93793c1949fc9cb6e
+Author: David Guibert <david.guibert@gmail.com>
+Date:   Fri Aug 5 14:20:12 2011 +0200
+
+    introduce module-dir
+
+diff --git a/depmod.c b/depmod.c
+index a1d2f8c..9362a35 100644
+--- a/depmod.c
++++ b/depmod.c
+@@ -48,9 +48,6 @@
+ 
+ #include "testing.h"
+ 
+-#ifndef MODULE_DIR
+-#define MODULE_DIR "/lib/modules/"
+-#endif
+ 
+ #ifndef MODULE_BUILTIN_KEY
+ #define MODULE_BUILTIN_KEY "built-in"
+@@ -1516,6 +1513,7 @@ static int parse_config_file(const char *filename,
+ 	char *line;
+ 	unsigned int linenum = 0;
+ 	FILE *cfile;
++ 	char *module_dir;
+ 
+ 	cfile = fopen(filename, "r");
+ 	if (!cfile) {
+@@ -1525,6 +1523,10 @@ static int parse_config_file(const char *filename,
+ 		return 0;
+ 	}
+ 
++        if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
++                module_dir = "/lib/modules/";
++        }
++
+ 	while ((line = getline_wrapped(cfile, &linenum)) != NULL) {
+ 		char *ptr = line;
+ 		char *cmd, *modname;
+@@ -1550,7 +1552,7 @@ static int parse_config_file(const char *filename,
+ 					continue;
+ 				}
+ 				nofail_asprintf(&dirname, "%s%s%s/%s", basedir,
+-					MODULE_DIR, kernelversion, search_path);
++					module_dir, kernelversion, search_path);
+ 				len = strlen(dirname);
+ 				*search = add_search(dirname, len, *search);
+ 				free(dirname);
+@@ -1565,7 +1567,7 @@ static int parse_config_file(const char *filename,
+ 				continue;
+ 
+ 			nofail_asprintf(&pathname, "%s%s%s/%s/%s.ko", basedir,
+-				MODULE_DIR, kernelversion, subdir, modname);
++				module_dir, kernelversion, subdir, modname);
+ 
+ 			*overrides = add_override(pathname, *overrides);
+ 			free(pathname);
+@@ -1737,6 +1739,7 @@ int main(int argc, char *argv[])
+ 	char *basedir = "", *dirname, *version;
+ 	char *system_map = NULL, *module_symvers = NULL;
+ 	int i;
++ 	char *module_dir;
+ 	const char *config = NULL;
+ 
+ 	if (native_endianness() == 0)
+@@ -1832,7 +1835,11 @@ int main(int argc, char *argv[])
+ 	if (optind == argc)
+ 		all = 1;
+ 
+-	nofail_asprintf(&dirname, "%s%s%s", basedir, MODULE_DIR, version);
++        if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
++                module_dir = "/lib/modules/";
++        }
++
++	nofail_asprintf(&dirname, "%s%s%s", basedir, module_dir, version);
+ 
+ 	if (maybe_all) {
+ 		if (!doing_stdout && !depfile_out_of_date(dirname))
+@@ -1850,7 +1857,7 @@ int main(int argc, char *argv[])
+ 		size_t len;
+ 
+ 		nofail_asprintf(&dirname, "%s%s%s/updates", basedir,
+-				MODULE_DIR, version);
++				module_dir, version);
+ 		len = strlen(dirname);
+ 		search = add_search(dirname, len, search);
+ 	}
+diff --git a/modinfo.c b/modinfo.c
+index 1dd8469..67b1041 100644
+--- a/modinfo.c
++++ b/modinfo.c
+@@ -19,9 +19,6 @@
+ #include "zlibsupport.h"
+ #include "testing.h"
+ 
+-#ifndef MODULE_DIR
+-#define MODULE_DIR "/lib/modules"
+-#endif
+ 
+ struct param
+ {
+@@ -193,6 +190,11 @@ static struct elf_file *grab_module(const char *name,
+ 	struct utsname buf;
+ 	char *depname, *p, *moddir;
+ 	struct elf_file *module;
++ 	char *module_dir;
++
++        if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
++                module_dir = "/lib/modules/";
++        }
+ 
+ 	if (strchr(name, '.') || strchr(name, '/')) {
+ 		module = grab_elf_file(name);
+@@ -207,9 +209,9 @@ static struct elf_file *grab_module(const char *name,
+ 		kernel = buf.release;
+ 	}
+ 	if (strlen(basedir))
+-		nofail_asprintf(&moddir, "%s/%s/%s", basedir, MODULE_DIR, kernel);
++		nofail_asprintf(&moddir, "%s/%s/%s", basedir, module_dir, kernel);
+ 	else
+-		nofail_asprintf(&moddir, "%s/%s", MODULE_DIR, kernel);
++		nofail_asprintf(&moddir, "%s/%s", module_dir, kernel);
+ 
+ 	/* Search for it in modules.dep. */
+ 	nofail_asprintf(&depname, "%s/%s", moddir, "modules.dep");
+diff --git a/modprobe.c b/modprobe.c
+index 5464f45..d9fbf9d 100644
+--- a/modprobe.c
++++ b/modprobe.c
+@@ -86,10 +86,6 @@ typedef enum
+ 
+ } modprobe_flags_t;
+ 
+-#ifndef MODULE_DIR
+-#define MODULE_DIR "/lib/modules"
+-#endif
+-
+ /**
+  * print_usage - output the prefered program usage
+  *
+@@ -2136,6 +2132,7 @@ int main(int argc, char *argv[])
+ 	struct modprobe_conf conf = {};
+ 
+ 	recursion_depth = 0;
++ 	char *module_dir = NULL;
+ 
+ 	/* Prepend options from environment. */
+ 	argv = merge_args(getenv("MODPROBE_OPTIONS"), argv, &argc);
+@@ -2233,7 +2230,11 @@ int main(int argc, char *argv[])
+ 	if (argc < optind + 1 && !dump_config && !list_only)
+ 		print_usage(argv[0]);
+ 
+-	nofail_asprintf(&dirname, "%s%s/%s", basedir, MODULE_DIR, buf.release);
++	if((module_dir = getenv("LINUX_MODULE_DIRECTORY")) == NULL) {
++		module_dir = "/lib/modules";
++	}
++
++	nofail_asprintf(&dirname, "%s%s/%s", basedir, module_dir, buf.release);
+ 
+ 	/* Old-style -t xxx wildcard?  Only with -l. */
+ 	if (list_only) {

gnu/system.scm

@@ -229,6 +229,7 @@ explicitly appear in OS."
 This is the GNU system.  Welcome.\n")
 
 (define* (etc-directory #:key
+                        kernel
                         (locale "C") (timezone "Europe/Paris")
                         (issue "Hello!\n")
                         (skeletons '())
@@ -255,6 +256,11 @@ export LC_ALL=\"" locale "\"
 export TZ=\"" timezone "\"
 export TZDIR=\"" tzdata "/share/zoneinfo\"
 
+# Tell 'modprobe' & co. where to look for modules.
+# XXX: The downside of doing it here is that when switching to a new config
+# without rebooting, this variable possibly becomes invalid.
+export LINUX_MODULE_DIRECTORY=" kernel "/lib/modules
+
 export PATH=$HOME/.guix-profile/bin:/run/current-system/profile/bin
 export PATH=/run/setuid-programs:/run/current-system/profile/sbin:$PATH
 export CPATH=$HOME/.guix-profile/include:" profile "/include
@@ -317,7 +323,8 @@ alias ll='ls -l'
                               (append-map service-pam-services services))))
        (profile-drv (operating-system-profile os))
        (skeletons   (operating-system-skeletons os)))
-   (etc-directory #:pam-services pam-services
+   (etc-directory #:kernel (operating-system-kernel os)
+                  #:pam-services pam-services
                   #:skeletons skeletons
                   #:issue (operating-system-issue os)
                   #:locale (operating-system-locale os)